A new equipment to test elongation thickening of highly concentrated suspensions and comparison of elongational with shear results

With a newly designed uni-axial elongation equiment, elongation thickening of highly concentrated suspensions was investigated. The equipment can measure the total tensile force and the liquid-phase pressure in the suspension. This allows to analyse all network stresses, i.e. all inter-particle stresses. Fro comparing elongation and shear properties, a rotational shear rehometer was equipped with facilities to simultaneously measure viscosity, liquid-phase pressure and normal force. The critical elongation rate beyond which dilatancy occurs is about a factor 30 lower than the corresponding shear equivalent. Especially in elongation and also in shear, the liquid phase pressure of the suspension decreases beyond a critical range.